Browsing by Author "Dutton, Jason L."
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Item A Computational Study on a Strategy for Isolating a Stable Cyclopentadienyl Cation(2014-10-20) Dutton, Jason L.; Wilson, David J.; Iversen, Kalon J.A computational study has been carried out to examine the feasibility of generating a simple monocyclic cyclopentadienylcation that may be sufficiently stable to isolate and handle at ambient temperatures. Using judicious placement of electron-withdrawing groups (CF3) about the ring we have identified a derivative that may approach the stability of isolobal (and isolatable) borole rings, as evaluated by HOMO–LUMO and singlet–triplet gaps. These Cp+ derivatives may therefore be an attractive target for synthetic isolation.
Item Access to the Parent Tetrakis(pyridine)gold(III) Trication, Facile Formation of Rare Au(III) Terminal Hydroxides, and Preliminary Studies of Biological Properties(2016-03-21) Dutton, Jason L.; Barnard, Peter J.; Hulett, Mark D.; Wilson, David J.; Hogan, Conor F.; Haghighatbin, Mohammad A.; Ryan, Gemma F.; Corbo, RobertIn this paper we report on the use of [NO][BF4] to access tricationic tetrakis(pyridine)gold(III) from Au powder, a species inaccessible using the more traditional (tetrahydrothiophene)AuCl route. It is then demonstrated that this family of compounds can be used to access new terminal Au(III) hydroxides, a challenging class of compounds, and the first crystallographically characterized examples employing bidentate ligands. Finally, preliminary biological studies indicate good activity for derivatives featuring polydentate ligands against the HeLa and PC3 cell lines but also strong inhibition of primary HUVEC cells.
Item Activation of the C–N Bond of N-heterocyclic Carbenes by Inorganic Elements(2014-09-14) Dutton, Jason L.; Wilson, David J.; Iversen, Kalon J.N-heterocyclic carbenes (NHCs) are generally considered to be extremely robust, ideal spectator ligands. However, in the past two years there have been several reports of the activation of the endocyclic C–N bond with subsequent insertion into element–hydrogen and element–carbon bonds. The new reaction pathway casts the reactivity of the NHC heterocyclic ring into a new light, especially in the context of potential catalyst decomposition. The synthetic reports and theoretical studies in this rapidly developing area are summarized here.
Item Facile Formation of Homoleptic Au(III) Trications via Simultaneous Oxidation and Ligand Delivery from [PhI(pyridine)2]2+(2014-09-03) Dutton, Jason L.; Barnard, Peter J.; Wilson, David J.; Hogan, Conor F.; Stringer, Bradley D.; Pell, Thomas P.; Corbo, RobertWe report the first examples of Au(III) tricationic complexes bound only by neutral monodentate ligands, which are a new class of gold reagents. Oxidative addition to the bis-pyridine Au(I) cation, [Au(4-DMAP)2]+, using a series of dicationic I(III) oxidants of the general form [PhI(L)2]2+ (L = pyridine, 4-DMAP, 4-cyanopyridine) allows ready access to homoleptic and pseudo-homoleptic Au(III) complexes [Au(4-DMAP)2(L)2]3+. The facile oxidative addition of Au(I) species additionally demonstrates the efficacy of PhI(L)2]2+ reagents as halide-free oxidants for Au(I). Comparisons are made via attempts to oxidize NHC-Au(I)Cl, where introduction of the chloride anion results in complex mixtures via ligand and chloride exchange, demonstrating the advantage of using the pyridine-based homoleptic compounds. The new Au(III) trications show intriguing reactivity with water, yielding dinuclear oxo-bridged and rare terminal Au(III)−OH complexes.
Item Heterobimetallic N‑Heterocyclic Carbene Complexes: A Synthetic, Spectroscopic, and Theoretical Study(2016-07-18) Barnard, Peter J.; Dutton, Jason L.; Skelton, Brian W.; Wilson, David J.; Pell, Thomas P.A new synthetic methodology has been developed for the preparation of heterobimetallic group 11 and group 12 complexes of a symmetrical bis-NHC “pincer” ligand. The synthetic route involved the initial preparation of a mononuclear [Au(NHC)2]+ complex with pendent imidazole moieties on the NHC ligands. Subsequent alkylation of the imidazole groups with Et3OBF4 and metalation with a second metal ion (Ag(I) or Hg(II)) provided two heterobimetallic complexes. Four homobimetallic (Cu(I)2, Ag(I)2, Au(I)2, and Hg(II)2) complexes of the same bis-NHC “pincer” ligand were also prepared. The homobimetallic Cu(I)2, Au(I)2, and Hg(II)2 complexes and heterobimetallic Au(I)−Ag(I) and Au(I)−Hg(II) complexes and the synthetic intermediates for the heterobimetallic complexes were characterized by X-ray crystallography. These X-ray structures show that the bimetallic complexes adopt “twisted” conformations in the solid state, supporting short M···M interactions. Crystalline samples of the homobimetallic Ag(I)2 and Au(I)2 and heterobimetallic Au(I)−Ag(I) and Au(I)−Hg(II) complexes were emissive at room temperature and at 77 K. The geometries of the synthesized complexes were optimized at the M06-L/def2-SVP level of theory, and the electronic nature of the M···M interactions for all synthesized complexes was investigated using natural bond orbital (NBO) calculations.
Item Investigating the Ring Expansion Reaction of Pentaphenylborole and an Azide(2014-10-11) Martin, Caleb D.; Dutton, Jason L.; Wilson, David J.; Thompson, Trevor K.; Couchman, Shannon A.The reaction between trimethylsilyl azide and pentaphenylborole was recently shown to produce the corresponding 1,2-azaborine. Investigating this transformation theoretically suggests that the reaction proceeds via coordination of the azide to the borole, rearrangement to a bicyclic species, and conversion to a kinetically favoured eightmembered BN3C4 heterocycle or expulsion of N2 to furnish the thermodynamically favoured 1,2-azaborine. The eight-membered species was structurally characterized as a borole adduct and represents an unusual analogue of cyclooctatetraene.
Item Is the Perfluorinated Trityl Cation Worth a Revisit? A Theoretical Study on the Lewis Acidities and Stabilities of Highly Halogenated Trityl Derivatives(2014-06-10) Dutton, Jason L.; Wilson, David J.; Couchman, Shannon A.The relative Lewis acidities of a series of known, unknown and observed but unstable halogenated derivatives of the trityl cation have been probed in a computational study. The Lewis acidity was investigated from hydride, fluoride and methide affinities. The results indicate that the perhalogen-ated trityl cation [C(C6F5)3]+ is a desirable synthetic target, especially in the modern age of weakly coordinating anions. Our results also indicate that the stable [C(C6Cl5)3]+ cation may be an equally interesting Lewis acid.
Item Probing the Reactivity of Pentaphenylborole with N–H, O–H, P–H, and S–H Bonds(2016-06-28) Martin, Caleb D.; Dutton, Jason L.; Wilson, David J.; Huang, Kexuan; Yruegas, SamThe reactions of molecules containing E–H functionalities (E = Group 15 or 16 element) and pentaphenylborole were investigated revealing diverse outcomes. For aniline and water, protodeborylation ring opening reactions occurred via the N–H or O–H bonds. Pentaphenylborole reacted with water in a 1 : 1 or 2 : 1 ratio to yield the corresponding boroxane and diboroxane, respectively, whereas aniline reacted strictly in a 1 : 1 ratio. Interestingly, 1-naphthalenethiol reacted to produce a 1-bora-cyclopent-3-ene heterocycle. The reaction with a primary phosphine generated an adduct which was resilient, even at elevated temperatures. DFT calculations provide support for the observed reaction products, and identify the initial adduct as a key intermediate in determining the final product. In particular, ring opening may be linked to the lability of the hydrogen in the initial adduct. Collectively, these reactions provide insight into new reaction pathways, the stability of boroles, as well as mechanistic insight into previously reported transformations.
Item Reactions of [PhI(pyridine)2]2+ with Model Pd and Pt II/IV Redox Couples(2014-02-03) Dutton, Jason L.; Wilson, David J.; Georgiou, Dayne C.; Corbo, RobertThe results of the reactions of the dicationic iodine(III) family of oxidants [PhI(pyridine)2]2+ with model Pd(II) and Pt(II) complexes are described. Depending on the specific reaction pairs, a variety of outcomes are observed. For palladium, Pd(IV) complexes cannot be observed but are implicated in C−C and C−N bond formation for Pd(II) starting materials based on phenylpyridine and 2,2-bipyridine, respectively. Theoretical comparisons with similar processes for −Cl and −OAc rather than pyridine indicate that these provide greater thermodynamic stability, and our results here show that they also give greater kinetic stability (the failure of MP2 methods for these systems is quite dramatic). In contrast, oxidation and delivery of the pyridine ligands gives dicationic Pt(IV) complexes that may be isolated and structurally characterized.
Item Reactivity of a Phosphaalkyne with Pentaarylboroles(2016-03-25) Martin, Caleb D.; Dutton, Jason L.; Wilson, David J.; Couchman, Shannon A.; Yruegas, Sam; Barnard, Jonathan H.The reactions of pentaarylboroles with 1-adamantylphosphaalkyne led to the formation of unique 1-phospha-6-boratricyclo-hept-3- enes. A rational mechanism for this transformation is proposed and supported by DFT calculations.
Item The First Bismuth–NHC Complexes(2014-01-14) Dutton, Jason L.; Wilson, David J.; Vin Tan, Kel; Corbo, Robert; Aprile, AntonioThe synthesis, isolation and crystallographic characterization of the first N-heterocyclic carbene adducts of bismuth is reported, by direct reaction of the Dipp2NHC (Dipp = 2,6-diisopropylphenyl) or iPr2(Me2)- NHC with BiCl3. This represents the last non-radioactive element from groups 13–17 for which an NHC– element fragment remained unreported.